1. Field of the Invention
Apparatuses and methods consistent with the present invention relate to digital content protection, and more particularly, to digital content protection in a digital rights management (DRM) system.
2. Description of the Related Art
With the shift from analog to digital technologies, more digital content has been produced. Whereas copying of analog content is tedious and time-consuming, copying of digital content is comparatively easy and can be performed faster than copying of analog content. In addition, the quality of analog content deteriorates in proportion to the number of copies executed, but the quality of digital content remains constant regardless of the number of copies executed. Accordingly, the demand for digital content protection has increased, and research into the field of content protection is being pursued.
FIG. 1 illustrates a conventional digital content protecting environment.
Referring to FIG. 1, in the conventional digital content protecting environment, a transmission stream is received through various broadcast transmitting channels, and content is protected from being copied by using information included in the transport stream.
One group, the CableLabs consortium, has recommended that content include copy control information (CCI) for controlling a content copy operation. The CCI is two-bit information that restricts the number of copies that can be made of content. The CCI defines a “copy free” state (00), a “copy once” state (01), a “copy no more” state (10), and a “copy never” state (11). The “copy free” state means that there are no restrictions on the number of copies that a user can make. The “copy once” state enables the user to make a single copy only. Once content is copied in the “copy once” state, the content has the “copy no more” state. The “copy never” state prohibits the user from making any copies of the content.
The United States Federal Communications Commission (FCC) has recommended that content be required to include a broadcast flag in order to prevent high-definition (HD) digital content that is broadcasted in the U.S. from being redistributed without restriction. The broadcast flag is one-bit information that indicates whether redistribution of content without restriction is prohibited. The broadcast flag includes a “broadcast flag on” state (1) and a “broadcast flag off” state (0). However, in the “broadcast flag on” state, the content is not allowed to be redistributed without restriction. In the “broadcast flag off” state, the content is allowed to be redistributed without restriction. Usage constraint information may include more pieces of information besides the above-mentioned information.
In order for a user to use a number of types of content pieces received through various transmission channels, the user must obtain a license from a copyright holder whenever using each content piece, which can be an inconvenient process. In this case, the content received through a transmission channel is imported by using a user's DRM system, the content is converted into a content file in accordance with a rule of the user's DRM system, and after a license is issued in accordance with original usage constraint information, the user can use the imported content file in a user's device or any device belonging to a user's domain.
Further, in the event that a single program includes a plurality of content parts, then a plurality of licenses is required. Although the content parts constitute one program, the content parts have independent usage constraint information. Thus, when the content parts are imported and stored as a content file, and when a user wants to use the content file in a device belonging to a user's domain, a transport packet constituting the content file has to be parsed in order to recognize the number of content parts constituting the content file. Then, licenses required for using each of the content parts have to be obtained, thereby resulting in time delay. In particular, the time delay increases even more when a device to use the content receives an imported content file in a streaming manner.